A Comprehensive Guide for Spray Painting Cardboard

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Spray painting on corrugated cardboard is kind of a big deal! Make artists express themselves on cardboards using spray-painting alone; if you search online you will be amazed what painters can do with spray paint and cardboard. But, spray painting on cardboard is not an easy job. Cardboard is made from kraft paper which is highly absorbent to liquid. Either it is to create an artwork or for craft or to simply repurpose your cardboard, you cannot work with cardboard alone. There is where the primer is used to create a barrier that can prevent the cardboard from soaking the paint. I’ve done some research and have compiled a comprehensive guide on spray painting on cardboard.

You could spray paint directly on the cardboard without using primer but it’s a tricky task and not just that it’s inefficient. However, we will discuss more on that later in the article. First, let’s start with the basics which are to apply primer on the cardboard.

How to Apply Primer on Cardboards?

You can either apply gesso, a type of primer used specifically by artists, or use a latex primer. There are oil based primers as well, but it will leave an oil patch or spots on the cardboard paper. With a primer, you can be assured that the spray paint on the cardboard will give its original appearance.

  1. Prep the surface on which you will apply primer on the cardboard. Spread some plastic sheets or cover the area with old newspapers. Primer is a brush-on application, so there won’t be much of a mess as with spray paint.
  2. Next, clean the cardboard surface for any oil, dirt or grease or tape adhesives. Then, wear your protective gear such as latex gloves, and goggle. You will need a nose mask as well while spray painting on the board.
  3. Use a polyester brush to paint a layer of latex primer. However, make sure to stir the primer in the can before applying as it could be sitting in the hardware store for a long time. Start by painting from the edges and then move to the center. It is typically done to prevent warping or curling of the cardboard. You could also use a paint roller if you are priming a large cardboard cutout.
  4. If you want to paint another layer of primer make sure the first layer is given enough time to dry. It is also advised to apply only a thin second layer of primer.
  5. If the primer is too coarse or rough, you can sand it down with fine sandpaper.
  6. Make sure the cardboard is cured properly before actually spray paint on the board.

How to Apply Gesso on Cardboard?

Gesso is a type of primer made from chalk, binder and another pigment which is used by artists to prime canvas and cardboard. It prevents the board from absorbing paint and brings out the color of the paint vividly.

  1. Prep the area by spreading out plastic sheets, drop cloth or tarp. You could also use old newspaper to protect the floor.
  2. Stir the can of gesso to make it consistent. It is mostly white in color; however, if you are looking for a colored primer, you can add a few drops of the acrylic color of your choice.
  3. Use a foam brush or a sponge to apply the first layer of gesso. Brush the cardboard with gesso, end-to-end, vertically. Let it dry for a day, then apply the second layer horizontally, again let it dry for a day. If the layer is too rough or course, you can sand it down using 500-grit sandpaper after it’s dry.

Instead of gesso, you can also prime the surface using white acrylic paint alone, but for that, you have to apply multiple thin layers of paint, giving enough time for the paint to dry in between. Furthermore, if you are using colored cardboard, you can use a clear gesso or similar transparent acrylic medium.

How to Spray Paint Cardboard?

Spray paint takes some patience and skill, moreover, with cardboard papers, you have to be more careful. Following are a few steps on how to spray paint on cardboard properly:

Step 1:

Before starting your spray paint, gather your material! You will need to drop clothes, old newspapers, some tape, a ventilator mask, gloves, and safety glasses.

Step 2:

Pick a workplace that has ample ventilation, such as your garage or even outdoor lawn is a great option. Next, make sure you have the right temperature, as spray paint don’t stick when it’s cold or humid.

Step 3:

Next, lay over a sheet of plastic or drop cloth or old newspapers; although newspapers may get soggy if exposed to too much spray paint. Also, cover other areas of the workplace where you don’t want spray paint. Tape off the areas of the cardboard where you don’t want to spray paint.

Step 4:

It is always better to keep your cardboard pieces resting on a wall or in a vertical position. Laying it on the surface doesn’t allow for good spray paint application. It would better if you could suspend the cardboard pieces using wires. On the other hand, if you are painting a cardboard box, it is advised to place it on a table or similar higher platform.

Step 5:

Next, clean the surface of the cardboard to remove any dirt, oil, great or tape gum and make sure it is completely dry before you apply your spray paint.

Step 6:

Put on your safety gear as well as ventilation mask. If you feel uneasy during spray paint, don’t stress out and take some rest.  Apply a coat of primer, as discussed earlier in the article. For gesso, you can even make your own at home, which we will explain later.

Step 7:

Shake the spray can before applying. It will allow the color and other pigments in the can to mix well. Give a test spray on other cardboard pieces or newspaper to see if the paint has the right consistency. This will also give you an idea of the distance you should maintain while painting the cardboard; the advised distance is 10 inches.

Step 8:

Apply your first coat, by spraying a thin layer of paint running parallel to the cardboard moving slowly from edge to edge. Avoid, focusing too much paint at one spot; it would either leave a patch or moisten the cardboard.

Step 9:

Let the first coat dry for a few hours or let it sit for a day. Then apply the second coat in a similar fashion to the right color. This will give you a chance to cover up any uneven paint in the first coat.

Step 10:

Let it dry for a day and apply a third sealer coat. It could a varnish or a clear coat; on which we will discuss next.

How to Apply a Varnish Coat on the Paint?

If you want to make your spray paint permanent, you should apply a clear varnish coat to preserve the paint. It will also make the cardboard weather resistant to some extent.

Varnish comes in clear gloss, satin or matte finish. If it’s a painting or a graffiti you should choose a gloss finish to bring out its colors. However, if it’s a solid paint to be used in the craft, you can have a matte finish to give it a dramatic effect. The varnish will significantly increase the life of the painted cardboard. However, if you want to photograph your paint on cardboard, you should do it now; after the varnish coat, it will give out significant glare making it difficult to photograph the painting.

  1. Prep the area by laying over drop cloth or old newspapers. Wear protective great and use separate container and a new brush to apply varnish.
  2. Now lay the painted cardboard flat on the floor or on a table. Dip the brush into the varnish a slightly over the tip and gently tap off any excess. Now apply the varnish in even strokes horizontally across the cardboard starting from edge to edge.
  3. Check your painted cardboard from an angle to see if any part of the cardboard is left out; the varnished area will give a glare in the light. If you see a speck of dust on the varnish, gently pull it out using a toothpick.
  4. Let the cardboard sit undisturbed for a few hours for the varnish to dry. 
  5. If you find the first coat to be thin, you could apply a second coat after the varnish has completely dried out; then let the second coat sit for a few hours to dry.

How to apply spray varnish?

  1. Wipe the cardboard surface to remove dirt, dust, etc. Prep the room by covering other stuff with drop cloth or tarp.
  2. Choose an open space outdoors to apply spray on varnish coat. Wear your ventilation mask, eye protection, gloves, etc.
  3. Place the painted cardboard vertically on a dust free surface. Mark off places with tapes where you don’t want your varnish.
  4. Shake the spray varnish can for a few minutes before applying on the cardboard.
  5. Apply the spray from at least 10 inches away at an even distance. Run the can parallel to the board from edge to edge.
  6. Keep checking the nozzle in between application for blockages. Varnish can clog up easily, so make sure to wipe off the nozzle from time to time.
  7. Apply a thin coat of varnish, let it dry for a few hours before applying the second coat.
  8. Spray on varnish will most likely give a better finish and sheen that brush-on varnish application.

Spray Painting on Cardboard without Using Primer

It’s a risky job but can be achieved, provided that the paint is acrylic or oil paint and you have an artist’s hand to work gently with patience. It usually takes multiple layers of colors before achieving the painting you want. If you are going to fill the whole cardboard with just one color, even then you have to apply multiple layers of paint, at the same time giving time for each layer to dry before the second layer.

If it were using a brush, the process could have been much simpler. With spray paint, you need good control over the nozzle and a swift hand so that you don’t spray too much on a single spot, which will leave an uneven patch or moist the cardboard, thereby destroying your project.

Without the primer, you have to apply a thin layer of spray paint coat on the cardboard so that the cardboard doesn’t soak up too much paint. The paint will look great immediately after applying the paint, but as you let it dry, you will notice that the cardboard has soaked up some paint, thereby leaving a pale color finish. Therefore, the spray paint is applied multiple times with a thin coat and a few hours to dry each time.

How to Prevent Cardboard from Warping or Curling?

Typically old cardboard boxes lock in moisture and may warp over time. Even after applying primer, you are likely to find warped cardboard. Moisture is the typical reason for warping or curling, be it because of the climate or water in paints. Many would seal their painted cardboard to protect it from moisture, but little do they know that if it’s based on PVA, it will sink in and warp the board.

The first step to prevent cardboard warping is getting rid of moisture or more technically keep the cardboard out of moisture. Even with a little humidity in the air will curl the cardboard marginally. Next, is to avoid using wet paint on the board, therefore it is advised to use enamels or acrylic paints. Even with acrylic, you have to apply a primer beforehand instead of spraying it directly on the board. A simpler solution would be to simply use thick cardboard that is double-walled or triple-walled.

If your cardboard is already warped, you can do a couple of things to flatten it out such as using weights. Lay out the warped cardboard with the warped side facing up. Make sure the base surface is flat; a table would work just fine. Now, place a sheet of flat plywood over the warped cardboard and put some weight on it. You can use a couple of books on each corner and some at the center. Metal tools, firewoods or bricks would also work. Let it sit for a few days and keep checking between a couple of days if the corrugated board has flattened out.

Spray Painting Best Practices

  1. Always start with a clean, dry surface. Make sure to sand or scrape any adhesives, dust, etc. Avoid using cardboards with oil and grease stains.
  2. Spray paint when the weather is right. Spray paint doesn’t work well with moisture, so pick a day when humidity is below 85% and the temperature is between  50°F and 90°F. Avoid direct sunlight or humid weather.
  3. Recoat a spray time after the first coat has dried out. Each manufacturer will have their own recoat time, which should be mentioned on the can.
  4. Spray painting is more of a skill than art. Test you spray painting technique on a black paper or discarded cardboard. You will know how to deal with corrugated cardboard while spray painting.
  5. Always spray paint a surface in one setting so that you get an even color tone. Use edge-to-edge painting running your spray can smoothly across the board.
  6. When working on corrugated cardboard, it is wise to work on multiple thin coats, keep the spray can at least 10 inches away from the board.
  7. Mask on areas with tape where you don’t want your paint.
  8. Always use a well-ventilated outdoor space to spray paint so that the fume circulate well. Furthermore, wear your safety gear such as a mask, safety glasses, and latex gloves.
  9. Give attention to the instructions that came with the spray can for optimum result.

Spray Painting Safety Tips

  1. Stay out of high heat and fire while spray painting. Keep away from sparks, open flame, pilot light, stoves, open electrical outlet and don’t smoke. Keep your spray can in a cool and dry place; avoid prolonged exposure to heat from the sun, radiator, stoves, etc.
  2. Don’t puncture or burn spray can. Dump it for recycling instead of discarding into the trash compactor.
  3. Wear respiratory protection and avoid prolonged exposure to spray paint fumes. Keep your workspace well ventilated.
  4. Check your electrical items for exposed wire, unplugged cords, open electrical outlets, etc.

Mask out the spray paint

If you want to spray paint simply for the reason of getting rid of those black labels on the box, then you should purchase mask-out spray paint. The paint has the same color as the corrugated cardboard box and doesn’t need any priming. Simply spray on the labels and symbols and instructions that came with the box and you are good to go.

Conclusion

Cardboard is made from kraft paper makes for an unsuitable substrate for spray paint. Still, you can’t stop people from doing that, because corrugated cardboard is abundantly available, inexpensive and sometimes free. It’s abundance and relative structural strength is what makes it an alternative to plywoods and canvas. You will even find many painters exclusively using corrugated cardboards to express themselves.

Either it is to spray paint a landscaper or graffiti or simply to repurpose like making a notice board, you will need to have patience and use the right equipment and paint for the job. You can spray paint any color you want, as long as it is acrylic; you can even give your cardboard a glittery golden or silver metallic or a black matte finish. If you are using it for craft, you can technically use any type of cardboard, but for painting, you should choose a thick double-wall or triple-wall cardboard.

Other than spray paints, you can spray coat a lot of things on cardboard such as varnish, waterproof coating, PVA glue, fiberglass resin, lacquer, etc. That is all you have to know to spray paint your cardboard, if you want to know more about the types of colors or paints you can use on cardboard, you can check out our other blog.

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